Electrical signaling system



May 28, 1946. R. R. BIRSS V v 2,400,909

ELECTRICAL S IGNAL ING SYSTEM Filed July 17, 1942 I I, I0

V INVENTOR ROBERT RAYMOND BIRSS ATTOR EY'.

signal to the u p u in such manner thatthey augment the received Patented May J u H acne-rarest S'IGNALINGSYSTEM, ammals li irss llarrogateiEngl and f 1 I Ta iuesnon my 17; 1942, Serial No; 451,306 v u urn Great Britain September as, 1941. t i e some (curve-51s) The present invention relatesto electrical signaling systems such as automatic telephone systems in which impulses are utilised to enact the positioning of selective apparatus and like operations and it is more particularly'concerned with arrangements for correcting impulse distortion whereby the operating range and capabilitlesoi t such systems may be increased. 'j p In systems where alternating current impulsins is employed distortion of the envelope oi each 1 signal impulse results ,due to the reactive characteristics of the line and also due to the presence of tuned filter circuitsat the 'signal receiving point, when these are provided. 'l'he'distortion usuallytakes the form of a dela inthe change of current at the beginning and end oteach impulseso that instead or possessingits original or thecharge and discharge or condenserthrough a resistance. 1 i t The invention has torits general obiect the equipment and the description oern itself withthis part. in

frequency signal receiver, connect withthe signal responsive apparatus via suitable tuned filter cir cults, not shown; and itwill he understood that i for correction purposes the signals will first be :rectifled andthen applied ,as direct current voltage pulses to terminals l0 and H across which is connected the rectifier network loadres'istance RI. Terminals I 0 and connect via resistance R2 to the grid' of theimpulse receivingvalve VI ideal rectangular form it has incremental and decremental slopes approximately, characteristic i the rectifier arrangement preceding-the arrange-i provision of a simple andefllcient method of cor it recting; distorted alternating current impulses. According to the invention alternating current signals received over a line arerectifled and appliedto two voltage responsive devices one of a which servesvto generate a voltage surge to sup plement the action 01 the second whereby a s'igs caused to operate rapidly.

nal responsive device controlled by the second is According to the invention a distorted alterhating current signalimpulse is rectifledand applied as a direct currentvoltafge signalto the grid oi" a voltage responsive valve connectedin' parallel with a signal voltage responsive valve Dropenthere being connected in theanodefcircult oi'the first valve the primarywlnding' o1 atranstormer, the arrangements beingsuch that voltagesurges areproduced inthe transformer secondar winding at commencement of the incremental and decremental slopesiofthe input signal which markthe beginning andend oi. the

in the anode circuit ofwhichis connectedthe impulsingrelay A, which is preferably of a high speed type.

VI is the valve V2 on to the grid of which a Connected in parallel with valve part of the inputis diverted via resistance R4.

"l'he-Aalternating current signal impulsesre ceivedover the line are essentially voltage signals and the direct current signals deliveredfroni ments shownin the drawing will therefore be slopes at their beginning and end similarto those of the incoming distorted alternating current signals. In order to efl'ect correction it is necessary to steepen the incremental and decremen- .30

tel slopes thereof,-and thisis effected by the additional valve V2 and the associated transiormer TR! connectedin the anode circuit thereof. The valve V2 serves asv atvoltage operated device adapted-to produce a varying current in its anode circuit corresponding to thevarylng voltageinput. This current in extending through transformer-"ml will cause surgevoltages to be prorluced in thesecondary winding during the transient conditionsat the commencement and-end original signal impulsethese voltage surges-being red attens applied in parallelwith thereoeived grid of the signal receiving valve signal input to this stage and produce a resulting or each impulse and these voltages arefed'hack I to the signal receiving-valve VI in such manner as to assist the signal input and so steepen the slopes of the envelopes oithe output signals delivered inits anodecircuitl. u I Reviewing the circuit; oper ti in mom g tail it will beunderstood that the grid of valve current signal in the anode circuit thereof have? in: incremental and arevery 'I'he correcting-devieeshown in the drawing is assumed to form the impulse receiving part or an alternating current signalreceiver adaptedto deliver direct current impulses to local receiving restr ow is VI is normallynegatively blessed with respect to its cathode bvmeans of the automatic bias re t 4 sistances RI and R1 to a value such -that;-the 1 normalanodecurrent flow is insumcient to oper i ate or hold relay A. while the grid of valve V2.

is similarly'biassed towards cut-oil" by-means oi the bias resistances R6 and R8. a

During the rise oi. voltage at commencement i of an applied directcurrent voltage impulse-that N D E rr 'r-io tj,

t V zsoosnsf I will merel con i The line over whichwalternating current signal impulses are received will in the case or a voice a carrier wave.

part or the input energy which is by-passed to the grid of valve V2 will gradually reduce the standing negative potential on its grid and an increasing current will flow in its anode circuit.

7 This currentin extending through the primary negative bias on the grid and so increase the anode current to a value such that relay A operate, but the positive feedback from trans-V former TRi has the effect of increasing the rate of change of grid voltage and so steepens the inicurrent flow. v 1-, At termination of the impulse, when the grid of valve VI commences gradually to return to its standing'negative value and so releases=relay A,

the positive feedback circuit comes into operation to increase the rate of restoration of the v standing grid voltage of valve VI. I

Another point which arises in connectionwith the positive feedback circuit from transformerh TRI is-that the feedback voltage in addition to beingapp'lied to the grid of valve Vi alsofinds a circuit on tothe grid of ,valve V2. The value of the feedback to valve, V2 will be kept below that at which oscillation .occurs by selection of th'eresistance values-RI, R2 and R3 which together form a potentialdivider circuit. giving an applied-voltage of p EXRl Rl+R2+R3 where E is the outputvoltage inthe secondary winding of transformerTBl, and it will beunderstood that in result the slopes of the signal delivered in the anode circuit of valve Vi are still further ste'epened.

Similar considerations apply for subsequent received impulses, the resulting output impulses in the anode circuit of valveVl becoming ones having incremental and decremental slopes'which are extremely steep and the output signalsdelivered by armature al of relay A onto leads. i8 and i1 therefore tend to approximate closely to an ideal rectangular form.

In the manner thus described theinvention enables correction of envelope distortion of alternating current impulses to'be effected, and in cases where filter networks are employed at .a receiving point it enables these to be of high selectivity types, the use of which has been hitherto not too desirable due to the envelope distortion effect they tended to produce.

The invention is moreover not limited to any pulsing, as the impulse's'may comprise a low fre- It will be appreciated that the invention is not limited solely to alternating current impulses but rather to any direct current impulses having substantial voltage changes with little or no current as occurs in the ease of the rectified output from tuned circuits'to which alternating current signals. are applied. A second stage correction could conveniently be eflected by the correcting device described in my co-pending application Ser. No. 451,305, filed Julyl'1,1942. V

I claim: a

1. In a signaling system, a signaling circuit upon which rectified alternating current signals .are impressed at times, a pair of voltage responsive devices each having an input circuit and an ou tputcircuit, means coupling the input circuits .tial rising slope of the wave formvoi the anode j v said devices are effective to energize their reof both devicesto said signaling circuit, whereby H the other of said devices,whereby the energization of said one dcvicesoutput circuit causes a voltage surgeto be generated in said other device's input circuit and therefore enhances'the energization of said other 'dev'lces output circuit. .2. In a signaling system, a pair'ofele'ct'rornc I valves each having a grid and 'a' plate circuit, a

common signal input to which the grids or both valves, are coupled, a responding device in'the platecircuit of one of said valves, means for impressing a direct current voltage upon said input therebyto cause said one valve to operate said device,- and a transformer having one winding connected'in the plate circuit or the other of said valves and'a' second winding connected to the grid of said one valve, thereby to increase thespeed 1 With'which said one valve operates said' device particular method of alternating-current imquency or high frequency alternating current transmitted either directly-or as'modulations on c g c The i invention is furthermore applicable to alternating current impulse repeatm arrangements aswell as to receivers.

' In' cases where the received signal is so distorted that the desired correction cannot be achieved in one stage it is possible that advantage responsive to said voltage being impressed upon said input. y

.3. Ina signaling system, a pair of electronic valves each having a grid and a plate circuit, a common signal input to which the, grids of both valves are coupled, a-responding device in the plate circuit of one of said valves, means for impressing a direct current voltage upon said input thereby to cause said one valve to operate said device, and an inductive link between the plate circuit of the other of said valves and the grid of said one valve thereby to provide'a positive feedback to said one valve for increasing the speed with which said one valve operates said device responsive'to said voltage being impressed upon said input.

4. In a signaling system, a pair ofelectronic' valves each having a grid and a plate circuit, a common signal input to which-the grids of both valves are coupled, a responding device in the plate circuit of one of said valves,means for impressing adirect current voltage upon said input thereby to cause said'one valve to operate said device, an inductive link between the plate circuit of the other of said valves and said common input thereby to provide a positive feedback to said one valve for increasing the speed with" which said one valve operates said device responsive to said voltage being impressed upon said input, and means for preventing, said inductivelink from causing said other valve to oscillate.

5. Ina signaling system, a signaling circuit upon which rectified altemating current signals are impressed at times. a pair of'voitage responsive devices each having an input circuit and an output circuit, means coupling the input circuits of both devices to said signaling circuit, whereby said devices are effective to energize their respective output circuits responsive to a rectified alternating current signal being impressed upon said signaling circuit, and means for inductively coupling the output circuit of one of said devices to the input circuit of the other of said devices thereby to quicken the energization and de-energization of said other device's output circuit.

6. In a signaling system, a pair of electronic valves each having a grid and a plate circuit, a common input to which the grids otboth valves are coupled, a responding device in the plate circuit of one of said valves. means for impressing a direct current voltage upon said input thereby to cause said one valve to operate said responding device, a positive fedback in the form of an in- 

